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s'rnrns FATENT rrrcst incnnosecsnr LAW? P Fl LAMENT.

SQPEUIFIGATIQN forming part of Letters Patent No. 464,719, dated December 8,1391.

Application filed J 2.1mm"; 2, 1890.

.5' 41-55 2071 0722, it vim con/corn:

' *nown that LUDWIG K. Bonn, of la, county of liew York, State of New York, have invented an Improvement in Processes of Making Filaments for Electric Lamps, of which the following dosoriptiom in. connection with the accom anying drawing, is a specification. fljibe invention relates to a process of makfilaments to emit li lit when by the passage we consisted of carbon, and a tile ai in to produce carbon for such filaments. it 0 been propos 3 by ou carbonaceous mat" sis in solutions l salts, sn b as chlorides and nitrates, carbonizi the same; but such proidesce s 1. p. A, a LG iodine 11122111162130 phases of the process strong mineral l;

t io acid'are set at ll ,r which are highly injurious to the filament and are likely to render the filament worthless for practical use in glowlamps. By other broposed processes filaments have been consisting of. carbon anda metalels Zor exam ple, aluminium and tungsten. In other processes a filament is first carbonized in the usual manner and is subsequently coated by the heating action of an electric current passing through it, in which case the coating is lilgely to peel off or break away from the filament when the current is passed through it after the filament has been removed from the liquid in which the coating is done.

The object of the present invention is to produce a filament of substantially different composition from those heretofore used, said filament consisting; of carbon and an oxide of the earth, alkali metals, preferably calcium or magnesium oxide; and the invention consists a filament having the composition stated and also in the process 05 making such filament, in which process no injurious decomposition products are formed, such as the strong mineral oxides above mentioned; but onthe otherliand the decomposition products are onlysuch are producedinthc ordinary Serial 1%. 385.652. (filo model.)

process of carbonizing' the materials commonly used n making filaments wholly of carbon, The filament composition of carbon, a conductive material, and calcin m oxide or magnesium. oxide, which are substantially non--con luctingand highly refractory materials, and when heated to incandescence by the passage of the current constitute a substantial part i the light-pro- (lacing agent. The conducting andnon-conducting rciractory substances are thoroughly combined and united so t form a compou having a sufficient conductivity to conveytlie current, but of far higher resistance th: n the conductive material the compound alone, and also havingfar greater light-emit ting capacity.

The pro erty of calcium oxide and. magne slum. oxide to admit light when lieated to in candescence is well known, this being the sub stance used in the Well-known lfirnmrnond light, in which such substances are heated by the org-dxydrcgen blovwpipe flame, and plaster-of-paris lias'been employed in a form of are light typified by tbe Well-known Jablochkoff candle, in which plaster-ofiparis 1s em ployed as an insulator to electrically separate the carbon electrodes between whichthe arc compound which has sufficient conductivity,- but is of higher resistance than fillQCOndlIGl? .ive material alone, and the proportions of the material in the compound may be varied so thus produced is a as'to produce any desired conductivity in a stead oi requiring long slender filaments to produce a higb. resistance to the current, as is thecase when the filaments are composed of substantially pure carbon or conductive material. I

In order to produce acarbon filament in accordance with this invention composed of conductive and non: conductive substances properly combined to afford an incandescent conductor of the required resistance, it is necessary to have thenon-conducting refractory substance evenly distributed throughout the filament, and when the filament is made by carbonizingthe conductive portion it is indispensable that the products of the decomposition arising during the process of carbon ization should not injure ,the filameht'as, is the casein processes in which the metal salts of strong mineral acids are used, in which processes the said acids are set at liberty, or by decomposition free chlorine is produced and the said acidsor chlorine attack and injure the material of the filaments.

The requirements for making a'compo und filament without injurious chemical action in the process of chemical action are fulfilled by the process forming the subject of this invention', in which the products of decomposition that arise during the process are entirely harmless, being the same as produced in carbonizing the fiber forming the basis of the filament in the usual process of making carbon filaments.

The compound filaments forming the subject of this invention are produced in the fol lowing manneri Freshly precipitated calcium carbonate ((32100 immediately after precipitation is dissolved by the passage of a strong current of carbonic-acid gas (CO lthrough itand produces soluble bicarbonate of calcium (CO llfiOa.

Then the thread that is to form'the conducting portion of the filament, and which may be of silk, linen, cotton, or other suitable material capable of c'arbonization, linen being (oounzoa:co,+n,o+caco,.

The thread is then carbonized in any usual manner, and the heat employed in this operation should be high enough to decompose the calcium carbonate, throwing oft carbonic-acid gas (00 and leaving in the filament calcium oxide, (GaO,) the chemical reaction being indicated'by the following formula: 00 0a: OO +Ga3, and owing to the presence of a large excess of carbon the carbon dioxide is decomposed, attacking the excessive carbon and forming carbon oxide '-C0 +C=2GO. As a result of this decomposition the calcium to incandescence by the passage of t rent through it. 'Thus a compound but ho mogeneous filament is produced by the carbonizing process, which is substantially different from a filament containing the same materials, but made from first forming the filament of carbon and subsequently apply- .ing to the carbonized filament other. materials to render it more refractory, such pro ,cesses resulting in a non-homogeneous filament which is likely to breaker separate into its component parts in its subsequent operation in the lamp. If the heat of the carbonizing-furnace is not sufiicientto fully decompose the calcium carbonate, as above E described, this will be efiected by the heat of the electric current while the lamp is in the process of manufacture. When desired, a larger portion of the refractory material may be embodied in the filament than can be introduced therein by soaking insoluble bicarbonate of calcium. This can be done by adding to the solution of bicarbonate of calcium some of the freshly-precipitated calcium car'- bonate. which is kept in suspension in the solution by adding gum-arabic to the solution and by passing a constant current of carbonicacid gas through the solution. It is especially desirab e to do this in the manufacture of filaments for series lamps, Which'are of comparatively Low resistance and are shorter and thicker than high-resistance filaments Gumarabic used as thusstated drieswhen the thread is dried, and serves to retain the calcium carbonate in the thread while being handled in the process of manufacture. The products given ofi in the decomposition of the bicarbonate and -carbonate -namely, vapor "of water and carbonic oxide and carbonic-acid gas oxid'eobyiously produce no injurious effect upon the material of thefila ment, since they are substantially the same as the products given ofi in the ordinary process of car'bonizing filaments. i

The herein-described materials may be compounded in various proportions, it being possible to make a homogeneous compound of carbon with a very large or very small proportion of calcium or magnesium oxide, and the proper proportions for any given filament may be determined by experiment, it being understood that other things being equal the resistance is greater the larger proportion of calcium or magnesium oxide incorporated in the compound. The drawing represents a filament composed of the conducting and non-conducting materials, and made by the process hereinbefore described, embodying,thxinvention.

I l m? 1. The process bi. making carbonizable material with carbonates'of calcium 01' magncsiumand carbonizing the same, Whcrcby a, filament is produced composed of carbcn and oxide of. calcium or magnesium,

substantially as described.

2. The herein-described improvement in the art or methcd of making filaments forinca'udescent lamps, which consists in scaking earbcnizabie material in a. solution of bicarbonate of calcium onmagnesium and subse- 

